Characterization of Glass Transition Temperatures for Stages of Sugar Cooking Utilizing a Model Sugar-Based Confectionary System

Presenting author: Melissa Wang

Co-authors: Shelly J. Schmidt

Department of Food Science and Human Nutrition

The stages of sugar cooking is a characterization system used throughout the confectionary industry, as well as in the home. It is comprised of six stages: thread, soft ball, firm ball, hard ball, soft crack, and hard crack. The characterization system typically includes physical property descriptions of each stage, cook temperature ranges, and example confections. This research proposes adding thermal behavior parameters to the characterization system, such as the glass transition temperature (Tg), since these parameters are indicative of material structure and textural behavior. Therefore, our objective is to investigate the thermal behavior of a model sugar-based confectionary system as a function of the six stages of sugar cooking, as well as representative confections from each sugar cooking stage. A model sugar-based confectionary system was used with a 70:30 ratio of sucrose to corn syrup and 70:30 ratio of solids to moisture. Samples were heated in open, copper-bottom pans over a gas range to each cook stage temperature (110°C, 115°C, 120°C, 125°C, 135°C, 150°C) and analyzed using a TA Instrument Q2000 Differential Scanning Calorimetry. Representative sugar-based confections from each sugar cooking stage, such as fondant, marshmallows, taffy, peanut brittle, and hard candy, were also analyzed. The Tg midpoint of the model system increased linearly from -26.85 to 41.75°C, as cooking temperature increased from thread to hard crack. The Tg midpoint of the confectionary products also increased linearly from -54.84 to 51.90°C, from soft ball to hard crack stages. These wide Tg ranges reflect the textural transformation from rubbery to glassy that these materials underwent as they progressed through the stages of sugar cooking. The Tg of the model system transitioned through room temperature between hard ball and soft ball stages; whereas, the Tg of the confectionary products transitioned through room temperature between soft crack and hard crack stages. The difference in textural behavior between the model system and confectionary products underscores the substantial role formulation plays in confection thermal behavior. Incorporating thermal behavior parameters into the stages of sugar cooking characterization system will both strengthen its scientific foundation and broaden its value as a tool for producing sugar-based confections.